Ask the Dietitian: Caffeine

Are you someone who needs coffee in the morning before you can function, or do you find if you have a cup of tea after 2pm it ruins your sleep? Caffeine and our reaction to it can be divisive. In this article we will be taking a closer look at how it can impact our bodies – the highs and the lows.

The pros of caffeine

First, let’s think about the pros of caffeine. Although there is no nutritional need for caffeine in the diet, many of us have a moderate intake of it throughout the day, starting with our morning coffee to help clear away our mental cobwebs. Caffeine can increase cognitive alertness, which can be particularly helpful in periods where we may be more sleep-deprived. There are also studies into caffeine and sport, with some suggesting that caffeine can reduce the perceived effort of some physical activities.

The cons of caffeine

There are, of course, downsides to caffeine. Pregnant women, for example, need to keep an eye on how much they consume, keeping to less than 200mg a day as large amounts of caffeine can increase the risk of complications. People with irritable bowel syndrome (IBS) may notice that caffeine triggers symptoms such as bloating and diarrhoea.

High levels of caffeine can affect us all, with symptoms such as increased anxiety, poor sleep and an irregular heartbeat. This, plus the fact that caffeine can interfere with calcium absorption, are all reasons why energy drinks (that contain large amounts of caffeine) are not suitable for children and teenagers, despite their popularity.

Finally, two other side effects of caffeine include a temporary increase in blood pressure, and an increase in the need to urinate. This increased urge is not enough to dehydrate us, but may present an inconvenience.

We can come to rely on caffeinated drinks, and if you have a high amount of caffeine in the diet and suddenly stop, it is likely that you will feel some withdrawal symptoms such as feeling irritable, having a headache and being more tired than usual. If you feel you are having too much, the best thing is to reduce the amount gradually.

How much caffeine should we have?

So how much caffeine is too much, and – with all the downsides – should we cut out caffeine altogether? As with most things it comes down to moderation. For non-pregnant, non-breastfeeding adults, the recommended safe limit is 400mg of caffeine a day (which is around four or five cups of coffee).

Here is a quick guide to some common sources of caffeine and the approximate caffeine content:

Tea: 45–50mg

Instant coffee: 60mg

Espresso: 80mg

Can of cola: 35–40mg

Energy drink (250mls*): 80mg

*Some cans of energy drink are larger than 250mls so will have more caffeine content.

As a dietitian, I would suggest having caffeine mindfully. Consider how it makes you feel, whether it gives you a pleasant mental boost, or whether it disrupts your sleep.

I would also consider how you consume it. For example, coffee also contains some fibre and is being increasingly researched for its health benefits; tea is also high in antioxidants. Other drinks can be high in sugar and may offer little additional nutritional benefit but might bring a sense of enjoyment. We rarely consume caffeine in isolation, so it is good to think about the food or drink you are consuming as a whole.

With that in mind, I’m going to go and put the kettle on!